GAP, France — Hurtling too fast for comfort down a twisty, turning foothill of the Alps, Tour de France leader Chris Froome faced a high-speed choice between risk and reward.

The Briton knew that 10 years ago on exactly the same descent, Joseba Beloki shattered his leg, elbow and wrist rounding a corner too fast and Lance Armstrong plowed into a field to avoid the prone Spaniard howling in pain.

So Froome wanted to go easy. Trouble was, Alberto Contador didn’t. Against his better instincts, Froome chased after his Spanish rival who sped down the treacherous stretch with asphalt made gooey and slippery by the July heat.

Just like Armstrong, flirting with disaster nearly cost Froome the Tour. Contador crashed as he rounded a right-hand corner, forcing Froome to swerve off the road, onto the grass and to put a foot down to stay upright.

Unlike Contador, who bloodied his right knee, Froome escaped with just a fright. Still, the drama on Tuesday's Stage 16 proved a point that Froome and his Sky team have made time and again: Despite his big lead, Froome won't savour victory until he's on the cobbles of the Champs-Elysees in Paris on Sunday.

"One second you could be going for the finish and about to win a race and the next you're lying in a ditch somewhere, with a broken bone," Froome said.

"I knew it was the descent where Beloki crashed so I was purposefully laying off a little bit and trying to take it easy but at the same time also trying to keep touch with the Saxobank guys who were really pushing the limits."

By that, Froome meant Contador and his Saxo-Tinkoff teammate from the Czech Republic, Roman Kreuziger, who are third and fourth in the overall standings but more than four minutes off the lead.

Opportunities for them to claw back are fast running out. The finish line in Paris is now just 415 miles and five days away. To their credit, they aren't simply accepting defeat but are harassing Froome all the way. If Froome wins, the way his rivals have repeatedly tested the British rider over the three weeks should give him the extra satisfaction of a victory hard-earned.

Stage 16 wound from Provence past vineyards, lavender fields and villages clinging to hillsides to the town of Gap, a staging post for what promises to be a grand finale in the Alps for the 100th Tour.

For a long while, it seemed as if the 104-mile trek to Gap from Vaison-la-Romaine, a charming town with old ruins near the Mont Ventoux where Froome won on Sunday, would be one of those Tour stages that don't amount to much.

Apparently preparing for the Alps, Froome and other main protagonists allowed 26 riders -- none of them a podium threat -- to escape far ahead. The stage winner, Rui Costa, later emerged from that group, riding away on the day's last climb, a 6-mile long ascent to Col de Manse, and then zipping down to Gap.

Although the Manse climb is less arduous and less steep than the Ventoux, where Froome blasted past Contador, the Spaniard and Kreuziger used to it test the Briton and his Australian wingman, Richie Porte. Several times, Contador tried accelerating away. Kreuziger did, too. But Porte and then Froome alone wouldn't let them get away.

To cool the asphalt, authorities doused the top of the climb with water. But Porte said the road down from there was sticky and slippery -- just as it was in the heat wave of 2003, when Beloki's back wheel slid away from him on a bend, hurling him to the ground. Armstrong went on to win that Tour -- only to have that and all six of his other victories in cycling's premier race stripped from him last year for doping.

On Tuesday, touching their brakes caused wheels to slip, Porte said.

"All of us had a bit of a moment coming down there, losing the front wheel, back wheel," he said.

"It was really difficult. In normal conditions I wouldn't have slipped like that, but it was very difficult terrain," said the 2007 and '09 champion, who was stripped of his '10 title for a failed doping test. "Sometimes you have to go for it, whether it's at the start or the end of a stage."

Froome said Contador "was taking too many risks."

"All teams are starting to get desperate now and they're taking uncalculated risks," he said. "In my opinion it was a bit dangerous from Alberto to ride like that, it's not good."

And there's worse to come. Thursday's Stage 18 not only includes a double ascent to the ski station of Alpe d'Huez, with its 21 hairpin bends, but also a harrowing descent that several riders have voiced concerns about.

Having seen that Froome wasn't completely comfortable chasing after Contador on Tuesday, the risk now is that his rivals could try to unsettle him again on Thursday's downhill from Col de Sarenne.

"It is a very dangerous descent. The road surface is not great," Froome said. "And there aren't any barriers on the corners, so if you go over the corner then you will fall down a long way. It's a dangerous descent and I hope the riders are aware of that, that they don't take risks like they did today."

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